TWI731769B - Composite photocatalyst material and preparation method thereof - Google Patents

Abstract

This creation provides a composite photocatalyst material and a preparation method thereof. The composite photocatalyst material comprises titanium dioxide, gold nano particles and sulfide quantum dots, and the gold nano particles and sulfide quantum dots are supported on the titanium dioxide; wherein, The sulfide quantum dots are lead sulfide quantum dots and zinc sulfide quantum dots, and the molar ratio of the sulfide quantum dots to the titanium dioxide is 0.1:1 to 0.3:1. The composite photocatalyst material of this creation has a low electron-hole recombination probability and can receive a light source with a wide wavelength range, and thus has an excellent hydrogen production efficiency.

Description

Composite photocatalyst material and preparation method thereof

This creation is about a photocatalyst material and its preparation method, especially a composite photocatalyst material and its preparation method that can be used for hydrolysis to produce hydrogen.

Since the industrial revolution, with the rapid development of science and technology, there has been an increasing reliance on fossil fuels, which have the advantages of easy access and high performance. However, excessive use of fossil fuels will emit a lot of greenhouse gases and harmful Gas causes environmental problems such as global warming, air pollution, and climate abnormalities. On the other hand, with the rapid increase in the world’s population, energy demand will inevitably increase, and with the limited global fossil fuel inventory, the source of energy supply is also facing severe challenges.

In order to avoid the environmental problems caused by the use of fossil fuels and the difficulties of increasingly depleted fossil fuels, countries all over the world are actively developing green energy sources that can be recycled in a sustainable manner, such as wind, tides, solar energy or water power, to replace petrochemical energy. However, Green energy is susceptible to the influence of innate topography, geographic location, and seasonal climate, which makes energy supply unstable. Therefore, compared with fossil fuels, it is still inadequate in practicality.

Another potential alternative to fossil fuels is hydrogen. The calorific value of hydrogen is about 14.19 × 10 ⁴ kJ/kg, which is about three times that of general fossil fuels (for example, gasoline is about 4.5 × 10 ⁴ kJ/kg). In addition, the combustion of hydrogen will only produce water but not carbon dioxide. Therefore, using hydrogen as a fuel not only has a good energy supply capacity, but also does not cause pollution to the environment. Accordingly, in recent years, methods for producing hydrogen without using petrochemical raw materials have been developed, such as water splitting by electrolysis and photoelectrochemical water splitting. Among them, the photoelectrochemical water splitting method is based on the photocatalyst after receiving light. , Decompose water through oxidation-reduction reaction to produce hydrogen.

Currently, the photocatalyst material commonly used to generate hydrogen is titanium dioxide (TiO ₂ ). However, the use of titanium dioxide as a photocatalyst still has many disadvantages. For example, the electrons generated by the excitation of the light source are easily recombined with the holes, and Only ultraviolet light (approximately only 5% of the sunlight spectrum) can be used as a light source for reaction and the like. Therefore, titanium dioxide has low efficiency in converting light energy into hydrogen gas and is difficult to be practical. In order to solve the above problems, some studies have pointed out that loading metal on titanium dioxide and then modifying it can reduce the occurrence of electron-hole recombination, and the wavelength range of the light source that can be used with is wider, but the wavelength range is still limited to ultraviolet light. In the range of visible light, the hydrogen production efficiency of the titanium dioxide photocatalyst material modified with metal is still not ideal. Accordingly, there is still a need to develop photocatalyst materials that can further improve the efficiency of hydrogen production to help the development of green energy.

In view of the above-mentioned defects in the prior art, the purpose of this creation is to provide a composite photocatalyst material with excellent hydrogen production efficiency.

To achieve the foregoing objective, this creation provides a composite photocatalyst material, which includes titanium dioxide, gold nanoparticles and sulfides quantum dots, and the gold nanoparticles and the sulfide quantum dots are supported On the titanium dioxide; wherein the sulfide quantum dots are lead sulfide quantum dots and zinc sulfide quantum dots, and the molar ratio of the sulfide quantum dots to the titanium dioxide is 0.1:1 to 0.3:1.

In this creation, by simultaneously loading gold nanoparticles and a specific proportion of sulfide quantum dots on titanium dioxide, it can not only greatly expand the applicable wavelength range of the light source, but also form a heterojunction structure to generate an appropriate potential gradient, which is beneficial to electrons and The separation of the electric holes allows the composite photocatalyst material of this creation to have excellent hydrogen production efficiency.

According to this creation, the quantum dot is a zero-dimensional nanomaterial, which means that the length, width, and height of the three-dimensional structure are all 1 nanometer (nm) to 100 nm in size. Preferably, the average size of the lead sulfide quantum dots is 5.5 nm to 6.0 nm; the average size of the zinc sulfide quantum dots is 5 nm to 6.5 nm.

Preferably, the molar ratio of the lead sulfide quantum dots to the zinc sulfide quantum dots is 1:1.

Preferably, the molar ratio of the sulfide quantum dots to the titanium dioxide is 0.1:1 to 0.2:1. More preferably, the molar ratio of the sulfide quantum dots to the titanium dioxide is 0.2:1. By further controlling the ratio of sulfide quantum dots to titanium dioxide in a specific range, the hydrogen production efficiency of the composite photocatalyst material can be further improved.

Preferably, the content of the titanium dioxide is taken as 100 parts by weight, and the content of the gold nanoparticles is 1 to 3 parts by weight. More preferably, the content of the titanium dioxide is taken as 100 parts by weight, and the content of the gold nanoparticles is 2 to 3 parts by weight. More preferably, the content of the titanium dioxide is taken as 100 parts by weight, and the content of the gold nano particles is 2 parts by weight. By further controlling the content of gold nanoparticles within a specific range, the hydrogen production efficiency of the composite photocatalyst material can be further improved.

Preferably, the hydrogen production efficiency of the composite photocatalyst material is 3300 micromole/g·h per hour to 5100 μmole/g·h per hour.

In addition, this creation also provides a method for preparing a composite photocatalyst material, which includes the following steps: Step (a): preparing a solution containing titanium dioxide and a chloroauric acid solution, and performing the chloroauric acid solution at 70°C to 90°C. The solution is added to the solution containing titanium dioxide to obtain a first mixed solution; step (b): heating the first mixed solution to 190°C to 210°C and holding the temperature for 7 to 9 hours to obtain the first composite material; Step (c): prepare a lead acetate solution and a zinc acetate solution, mix the lead acetate solution and the zinc acetate solution, and then add the first composite material to obtain a second mixed solution; step (d): in the second mixed solution The sodium sulfide solution is added to the sodium sulfide solution and then the hydrothermal reaction is performed to obtain the second composite material, wherein the reaction temperature of the hydrothermal reaction is 120°C to 180°C, and the reaction time is 23 hours to 25 hours; and step (e): drying The second composite material to obtain the composite photocatalyst material; wherein the composite photocatalyst material includes titanium dioxide, gold nano particles and sulfide quantum dots, and the gold nano particles and the sulfide quantum dots are supported on the titanium dioxide The sulfide quantum dots are lead sulfide quantum dots and zinc sulfide quantum dots, and the molar ratio of the sulfide quantum dots to the titanium dioxide is 0.1:1 to 0.3:1.

By controlling the reaction temperature of the hydrothermal reaction in a specific range, the formed sulfide quantum dots can be uniformly loaded on the titanium dioxide without significant agglomeration. In addition, by making the titanium dioxide loaded with gold nanoparticles As well as the technical means of a specific ratio of sulfide quantum dots, the composite photocatalyst material prepared by the preparation method provided by this creation can have excellent hydrogen production efficiency.

Preferably, in step (d), the reaction temperature of the hydrothermal reaction is 120°C to 140°C. More preferably, in step (d), the reaction temperature of the hydrothermal reaction is 120°C. By further controlling the reaction temperature of the hydrothermal reaction within a specific range, the sulfide quantum dots supported on the titanium dioxide can be more uniformly dispersed, and the hydrogen production efficiency of the composite photocatalyst material can be further improved.

Preferably, in step (a), the chloroauric acid solution is added to the solution containing titanium dioxide at a rate of 2 ml/min to 3 ml/min.

Preferably, in step (a), the pH value of the solution containing titanium dioxide is 5.5 to 6.5, and the pH value of the chloroauric acid solution is 7.5 to 8.5.

Preferably, in step (c), the concentration of the lead acetate solution and the zinc acetate solution are the same.

Preferably, in step (d), the addition amount of the sodium sulfide solution is 2.5 to 3 times the volume of the second mixed solution. More preferably, in step (d), the concentration of the sodium sulfide solution is the same as the concentration of the lead acetate solution and/or zinc acetate solution, and the added amount is 2.5 to 3 times the volume of the second mixed solution.

In the description, the range represented by "decimal value to large value", if not specified, means that the range is greater than or equal to the small value to less than or equal to the large value. For example: 0.1:1 to 0.3:1, which means "greater than or equal to 0.1:1 to less than or equal to 0.3:1".

Specific examples are listed below to illustrate the implementation of creation. Those who are familiar with this art can easily understand the advantages and effects of creation through the content of this manual, and make various modifications and changes without departing from the spirit of creation for implementation. Or application creation content.

The following are the brands and models of the instruments used in the examples and reference examples: 1. Transmission Electron Microscope (Analytical Scanning Transmission Electron Microscope, ASTM): JEOL JEM-3010; 2. Ultra-high Resolution Field-emission Scanning Electron Microscope (FE-SEM): AURIGA JEOL6330; 3. X-ray Diffractometer (XRD): BRUKER D8 Discover; 4. Ultraviolet-Visible-Near Infrared (UV-Vis-NIR): JASCO V-670; 5. Photoluminescence (PL): HITACHI F-4500; 6. Gas Chromatograph-Thermal Conductivity Detector (GC-TCD): YL-instrument 6500 GC system; 7. Solar simulator: MKS 66483-300XF-R22; 8. Freeze dryer: EYE4 FDU-1200; 9. Ultrasonic oscillator: DELTA DC200H.

The following are the raw materials used in the examples and reference examples: 1. Titanium dioxide (P25): purchased from Degussa; purity is 99%; 2. Gold chlorate trihydrate: purchased from Alfa Aesar; purity greater than 49.9%; 3. Zinc acetate: purchased from SHOWA; purity greater than 99%; 4. Lead acetate: purchased from Alfa Aesar; purity greater than 99%; 5. Sodium sulfide: purchased from ACROS; purity greater than 98%; 6. Sodium hydroxide: purchased from SHOWA; purity greater than 97%; 7. Ammonia: purchased from SHOWA; purity greater than 28%; 8. Methanol: purchased from Fisher Brabd; purity greater than 99%.

Example 1 to 12 ：Composite photocatalyst material

Weigh 0.3995 g of titanium dioxide (P25) and disperse it in 100 ml of deionized water, then adjust the pH to 6 with a concentration of 1 M aqueous ammonia solution to obtain a solution containing titanium dioxide; weigh out 7.99 mg of chloric acid trihydrate The gold is dissolved in 100 ml of deionized water, and the pH value is adjusted to 8 with a 0.1 M sodium hydroxide solution to obtain a chloroauric acid solution. Next, place the solution containing titanium dioxide in a water bath at 80°C, and add the chloroauric acid solution to the solution at a rate of 2 ml to 3 ml per minute while the agitator is stirred at 500 rpm. The solution containing titanium dioxide is then continuously stirred for 2 hours to obtain a first mixed solution. After that, the first mixed solution was placed in a high-temperature furnace and heated at 200°C for 8 hours. After completion, the obtained powder was heated in a mortar at room temperature (about 25°C). Grind for 10 minutes to obtain a first composite material, the first composite material is titanium dioxide loaded with gold nanoparticles, and the content of titanium dioxide is taken as 100 parts by weight, and the content of gold nanoparticles is 2 parts by weight.

Weigh an appropriate amount of zinc acetate into a 50 ml beaker, add 25 ml of deionized water, shake and stir evenly to obtain a zinc acetate solution; also weigh an appropriate amount of lead acetate into a 50 ml beaker, and add 25 ml of deionized water was shaken and evenly stirred to obtain the lead acetate solution, and then 12.5 ml of the aforementioned zinc acetate solution and 12.5 ml of the aforementioned lead acetate solution were put into a beaker, and after shaking and stirring, evenly mixed, then added to the aforementioned For the first composite material, continue shaking and stirring for 30 minutes, and then add a sodium sulfide solution with the same concentration as the lead acetate solution and the zinc acetate solution and a total volume of 62.5 ml at a rate of 2 ml to 3 ml per minute. Subsequently, stirring was continued for 2 hours to obtain a second mixed solution.

The aforementioned second mixed solution was put into an autoclave for a hydrothermal reaction for 24 hours, and after the reaction was completed, it was cooled to room temperature, and the precipitate was taken out to obtain the second composite material. Next, the aforementioned second composite material was washed 3 times with water and then freeze-dried for 16 hours. The freeze-dried powder was ground in a mortar at room temperature (approximately 25°C) for 10 minutes to obtain Example 1 Compound photocatalyst materials up to 12.

The addition amount of zinc acetate, the addition amount of lead acetate, the reaction temperature of the hydrothermal reaction, and the molar ratio of sulfide quantum dots to titanium dioxide used in the preparation process of Examples 1 to 12 are listed in Table 1 below. Table 1: The addition amount of zinc acetate, the addition amount of lead acetate, the reaction temperature of the hydrothermal reaction and the molar ratio of sulfide quantum dots to titanium dioxide used in Examples 1 to 12 Example number Addition of zinc acetate ( g / 50ml water ) Lead acetate addition amount ( g / 50ml water ) Reaction temperature of hydrothermal reaction (℃) The molar ratio of sulfide quantum dots to titanium dioxide Example 1 0.0549 0.0813 120 0.1:1 Example 2 140 0.1:1 Example 3 160 0.1:1 Example 4 180 0.1:1 Example 5 0.1098 0.1626 120 0.2:1 Example 6 140 0.2:1 Example 7 160 0.2:1 Example 8 180 0.2:1 Example 9 0.1647 0.2439 120 0.3:1 Example 10 140 0.3:1 Example 11 160 0.3:1 Example 12 180 0.3:1

Comparative example 1 :Titanium dioxide

In Comparative Example 1, titanium dioxide (P25) purchased from Degussa was selected as the photocatalyst material in the prior art. Among them, titanium dioxide (P25) refers to P25 type titanium dioxide, which contains about 80% anatase titanium dioxide and about 20%. Rutile titanium dioxide.

Comparative example 2 ：Titanium dioxide modified by gold nanoparticles

The preparation process of Comparative Example 2 is roughly the same as that of Examples 1 to 12. The main difference is that Comparative Example 2 only carried out the step of loading gold nanoparticles on titanium dioxide, and did not further carry out the loading of sulfide quantum dots on gold Nanoparticle modification of titanium dioxide on the steps.

The specific preparation process of Comparative Example 2 is to weigh 0.3995 g of titanium dioxide (P25) and disperse it in 100 ml of deionized water, and then adjust the pH to 6 with a 1 M aqueous ammonia solution to obtain a solution containing titanium dioxide; Dissolve 7.99 mg of gold chlorate trihydrate in 100 ml of deionized water, and adjust the pH to 8 with a concentration of 0.1 M sodium hydroxide solution to obtain a chloroauric acid solution. Next, place the solution containing titanium dioxide in a water bath at 80°C, and add the chloroauric acid solution to the solution at a rate of 2 ml to 3 ml per minute while the agitator is stirred at 500 rpm. The solution containing titanium dioxide was then continuously stirred for 2 hours, and then placed in a high-temperature furnace and heated at 200°C for 8 hours. After completion, the powder obtained was placed at room temperature (about 25 Grinding was carried out in a mortar for 10 minutes at ℃) to obtain the gold nanoparticle-modified titanium dioxide of Comparative Example 1, and the content of titanium dioxide was taken as 100 parts by weight, and the content of gold nanoparticle was 2 parts by weight.

analysis 1 ：Analysis of the microstructure, surface morphology and elemental composition of composite photocatalyst materials

Take ASTEM to observe the microstructure of the composite photocatalyst material of each embodiment and use Energy-dispersive X-ray spectroscopy (EDS) for elemental composition analysis, and take Example 5 as an example. The results are shown in Figure 1. Show. From Fig. 1, it can be clearly observed that gold nanoparticles, zinc sulfide quantum dots, and lead sulfide quantum dots are supported on titanium dioxide. Among them, the gold nanoparticle is in the shape of a sphere, the shape of the zinc sulfide quantum dot is approximately spherical, and that of lead sulfide The shape of the quantum dots is approximately triangular, and after measurement, the average particle size of gold nano particles is about 10 nm, the average particle size of zinc sulfide quantum dots is about 5.2 nm to 6.41 nm, and the average particle size of lead sulfide quantum dots The diameter is about 5.63 nm to 5.89 nm. Looking at the results of elemental composition analysis, as shown in Figure 2, in addition to the copper and carbon contained in the carbon-coated copper mesh as the supporting substrate, only titanium, oxygen, zinc, gold, and lead are observed. It can be proved that the composite photocatalyst material of Example 5 does have gold nano particles, zinc sulfide quantum dots, and lead sulfide quantum dots supported on titanium dioxide.

The FE-SEM was used to observe the surface morphologies of Examples 5 to 8 at a magnification of 50,000 times, and the results are shown in FIGS. 3A to 3D, respectively. Figures 3A to 3C all present similar patterns, that is, it can be observed that approximately circular particles are stacked on each other. In Figure 3D, it can be observed that in addition to stacking on each other, slight agglomeration of particles also occurs. It is presumed that it should be implemented. Example 8 is caused by the use of a higher temperature for the hydrothermal reaction. Furthermore, FE-SEM was used to analyze the elemental composition of Example 5 at a magnification of 5,000 times, and the results are shown in FIGS. 4A to 4F. From the results in Figures 4B to 4F, it can be clearly observed that titanium, oxygen, zinc, sulfur, and lead all present clear signals, and the distribution patterns of the signals also show that the zinc sulfide quantum dots and lead sulfide quantum dots are indeed Evenly loaded on titanium dioxide.

analysis 2 ：Analysis of chemical composition and crystal structure

The crystal phase structure of the composite photocatalyst material of each example was analyzed by XRD, and the results of Examples 5 to 8 were taken as examples for illustration. The results are shown in FIG. 5. According to the XRD patterns of different substances listed by the Joint Committee on Powder Diffraction Standards (JCPDS), the characteristic peaks of anatase titanium dioxide can be observed from the results in Figure 5: 2θ=24.8°, 37.3 °, 47.6°, 53.5°, 55.1°, 62.2°, which correspond to the crystal planes (101), (004), (200), (105), (211) respectively (JCPDS card number: 21-1272); gold The characteristic peaks of redstone titanium dioxide: 2θ=7.0°, 36.5°, 40.8°, 54.0°, 53.9°, 56.1°, 61.0°, which correspond to (110), (101), (200), (111) ), (210), (211), (220), (002), (310) crystal planes (JCPDS card number: 21-1276); characteristic peaks of gold element: 2θ=38.2°, 44.4°, 64.5°, They correspond to the crystal planes (211), (200), (213) (JCPDS card number: 04-0784); the characteristic peaks of zinc sulfide: 2θ=27.2°, 28.8°, 30.9°, 48.1° (JCPDS card number: 80-0007); and the characteristic peaks of lead sulfide: 2θ=26.0°, 30.1°, 43.1°, 51.0° (JCPDS card number: 05-0592). In Figure 5, since the 26.0° characteristic peak representing lead sulfide is quite close to the 27.0° characteristic peak representing anatase titanium dioxide, there is only an overlapping characteristic peak with higher intensity at about 26.0° in the figure; similar Ground, because the 28.8° characteristic peak representing zinc sulfide is quite close to the 30.1° characteristic peak representing lead sulfide, there is also only an overlapping characteristic peak with higher intensity at about 30.0° in the figure.

In addition, from the XRD patterns of Examples 5 to 8, it can also be observed that as the reaction temperature during the hydrothermal reaction increases, the peak intensity of each peak also increases, indicating that as the reaction temperature of the hydrothermal reaction increases, The integrity of the crystal form can be improved.

analysis 3 : Wavelength analysis of the light source that can be used

A UV-Vis-NIR analyzer was used to analyze the wavelength range of the light source that can be used in Examples 1 to 12, Comparative Example 1 and Comparative Example 2. The measured light source wavelength range is 300 nm to 1800 nm, and the results are shown in Figures 6A to 6D Among them, FIG. 6A only takes the result of Example 5 as a representative and illustrates the difference between Comparative Example 1 and Comparative Example 2.

From the results in Figure 6A, it can be seen that Comparative Example 1 only has an absorption peak at a wavelength of about 380 nm to 400 nm. When the wavelength of the light source is higher than 400 nm, no absorption peak is observed, that is, Comparative Example 1 can only receive ultraviolet light. Light source in the wavelength range; referring to the results of Comparative Example 2, in addition to the absorption peak at a wavelength of about 380 nm to 400 nm, an obvious absorption peak can also be observed at a wavelength of about 580 nm, showing that Comparative Example 2 is transparent Loading gold nanoparticles on titanium dioxide can increase the wavelength range of the light source that it can receive. However, when the wavelength is higher than 600 nm, the absorption value exhibited by it is significantly reduced; in contrast to the results of Example 5, It exhibits a relatively high absorption value in the wavelength range of 300 nm to 1800 nm, showing that no matter the light source of ultraviolet light, visible light or infrared light can be used by the composite photocatalyst material of this creation, it can be confirmed that the relative Compared with the titanium dioxide of Comparative Example 1 and the titanium dioxide modified by the gold nanoparticles of Comparative Example 2, Example 5 does have the best usable light source wavelength range.

Further referring to the results of FIGS. 6B to 6D, it can be seen that Examples 1 to 12 have similar results for the wavelength range of the light source that can be used, that is, it has good absorption capacity for light sources such as ultraviolet light, visible light, and infrared light. It can be proved that the composite photocatalyst material of this creation can indeed use light sources with a wider wavelength range.

analysis 4 ：The energy gap change of composite photocatalyst materials

A UV-Vis-NIR analyzer was used to analyze Examples 1 to 12 and make Tauc curves to understand the energy gap changes of titanium dioxide loaded with gold nanoparticles and sulfide quantum dots at the same time. The results are shown in Figs. 7A to 7C. In the composite photocatalyst materials of Examples 1 to 12, it can be observed that there are two energy gaps, and the lower energy gap (left in the figure) is the energy gap of lead sulfide quantum dots, and the higher energy gap (in the figure) On the right) is the energy gap of titanium dioxide. Further observation of the results in Figure 7A shows that when the molar ratio of sulfide quantum dots to titanium dioxide titanium is 0.1:1 (Examples 1 to 4), as the reaction temperature of the hydrothermal reaction decreases, the energy gap of titanium dioxide decreases from 3.17 eV is reduced to 2.80 eV, and the energy gap of lead sulfide quantum dots is increased from 0.57 eV to 0.94 eV. From the results in Figure 7B, it can be seen that when the molar ratio of sulfide quantum dots to carbon dioxide titanium is 0.2:1 (Example 5 to 8), as the reaction temperature of the hydrothermal reaction decreases, the energy gap of titanium dioxide decreases from 3.14 eV to 2.14 eV, and the energy gap of lead sulfide quantum dots increases from 0.80 eV to 0.92 eV; and the results from Figure 7C It can be observed that when the molar ratio of sulfide quantum dots to titanium dioxide titanium is 0.3:1 (Examples 9 to 12), as the reaction temperature of the hydrothermal reaction decreases, the energy gap of titanium dioxide decreases from 1.90 eV to 1.42 eV. The energy gap of lead sulfide quantum dots increased from 0.82 eV to 0.89 eV. It can be seen from this that when the content of sulfide quantum dots is fixed, lowering the reaction temperature of the hydrothermal reaction can reduce the energy gap of titanium dioxide.

In addition, when the reaction temperature of the hydrothermal reaction is fixed, as the content of sulfide quantum dots increases, the energy gap of titanium dioxide will also decrease. Take Example 1 (the molar ratio is 0.1:1 ), the results of Example 5 (molar ratio 0.2:1) and Example 9 (molar ratio 0.3:1) are taken as examples. When the reaction temperature of the hydrothermal reaction is all 120°C, the energy of titanium dioxide The gap is 2.80 eV, 2.14 eV, and 1.63 eV in order, indeed showing a downward trend.

analysis 5 :electronic - Analysis of the degree of electrical hole recombination

The degree of electron-hole recombination in Examples 1 to 12, Comparative Example 1 and Comparative Example 2 after being excited by a light source was analyzed by a light-induced fluorescence spectrometer. The test method is to use a light source with a wavelength of 580 nm for excitation, and then use The intensity of the fluorescence emitted by electrons from the ground state to the excited state and back to the ground state can be used as the basis for judging the degree of electron-hole recombination. Among them, the stronger the peak measured by the light-induced fluorescence spectrometer represents the fluorescence The greater the light intensity, the higher the degree of electron-hole recombination, otherwise it can be judged that the degree of electron-hole recombination is low. The results are shown in Figs. 8A to 8D, among which Fig. 8A only uses the result of Example 5. It is representative and explains the differences from Comparative Example 1 and Comparative Example 2.

It can be observed from Fig. 8A that Comparative Example 1 has a higher fluorescence intensity in the wavelength range of about 350 nm to 550 nm, especially at a wavelength of about 550 nm, a very obvious peak can be seen and has a strong Fluorescence intensity shows that the electron-hole recombination degree of Comparative Example 1 is very high after being excited by the light source. Looking at the results of Comparative Example 2, no significant difference is observed in the wavelength range of about 350 nm to 550 nm. The peak and the fluorescence intensity are low. In addition, the fluorescence intensity of the more obvious peak at the wavelength of about 550 nm is also greatly reduced. It shows that the comparative example 2 can reduce electron-electricity by loading gold nanoparticles on titanium dioxide. Probability of hole recombination; referring to the results of Example 5 again, it shows that no obvious peaks are observed in the wavelength range of about 350 nm to 550 nm, and the overall fluorescence intensity is lower than that of Comparative Example 2. , And the peak at a wavelength of about 550 nm further reduces its fluorescent intensity. It can be confirmed that compared with the titanium dioxide of Comparative Example 1 and the titanium dioxide modified by the gold nanoparticles of Comparative Example 2, the examples 5 The degree of electron-hole recombination after being excited by the light source is indeed the lowest.

Further referring to the results of Figures 8B to 8D, it can be seen that the fluorescence intensity measured in Examples 1 to 12 after being excited by the light source all show similar results, and the highest fluorescence intensity of these groups is not higher than 600 au, approximately Only half of the highest fluorescence intensity (over 1000 au) of Comparative Example 2. It can be confirmed that the composite photocatalyst material of this creation has the characteristics of low electron-hole recombination.

analysis 6 : Hydrogen production efficiency test

Use a 300-watt solar simulator with AM 1.5 G filter as the illumination light source, and select 50 mg of the photocatalyst materials of Examples 1, 5 to 9, Comparative Example 1 and Comparative Example 2 to dissolve in water and use volume percentages Methanol with a concentration of 20% was used as a sacrificial reagent for photocatalytic hydrolysis and hydrogen production test, and then the gas produced by the reaction was extracted every hour with a gas needle, and then the hydrogen content was analyzed by a gas chromatograph.

The results of the hydrogen production efficiency test are shown in FIG. 9. Here, only the results of Example 5 and the results of Comparative Example 1 and Comparative Example 2 are selected for exemplary description. It can be clearly observed from the comparison result of Figure 9 that when the test is carried out to 1 hour, the hydrogen production of Example 5 is significantly higher than that of Comparative Example 1 and Comparative Example 2, and as the test time increases to 5 hours, Example The cumulative amount of hydrogen produced by 5 has far exceeded that of Comparative Example 1 and Comparative Example 2. It can be seen that, compared with Comparative Example 1 and Comparative Example 2, Example 5 does have better hydrogen production efficiency.

Then, the cumulative hydrogen production of each group for 5 hours was divided by the total time to obtain the average hydrogen production per hour to facilitate the evaluation of the hydrogen production efficiency of the photocatalyst material. Examples 1, 5 to 9, Comparative Example 1 and Comparison The hydrogen production efficiency of Example 2 is listed in Table 2 below. The results in Table 2 show that the hydrogen production efficiency of Examples 1, 5 to 9 is at least higher than 3300 μmol/g･h, among which the hydrogen production efficiency of Example 5 reaches 5011 μmol/g･h. In contrast, Comparative Example 1 As well as the hydrogen production efficiency of Comparative Example 2, Comparative Example 1 is only 84.56 μmol/g･h, and Comparative Example 2 only increases the hydrogen production efficiency to 2715 μmol/g･h through the technical means of supporting gold nanoparticles. It can be confirmed that the composite photocatalyst material of this invention does have a very good hydrogen production efficiency. Table 2: The hydrogen production efficiency of Examples 1, 5 to 9, Comparative Example 1 and Comparative Example 2. Example number Hydrogen production efficiency (μmol/g ･ h) Example 1 4309 Example 5 5011 Example 6 4389 Example 7 3918 Example 8 3407 Example 9 3624 Comparative example 1 84.56 Comparative example 2 2715

In summary, the composite photocatalyst material provided by this creation has a specific composition of titanium dioxide, gold nanoparticles and a specific proportion of sulfide quantum dots. In addition to expanding the wavelength range of the light source, it can also reduce electron-electricity. The hole recombination probability, so it has a very excellent hydrogen production efficiency, can be further applied to the development of green energy, has a very high development potential and value.

The above-mentioned embodiments are merely examples for the convenience of description, but this embodiment is not used to limit the scope of patent application for this creation; anyone with common knowledge in the technical field should be able to do so without departing from the scope of the technical solution for this creation. Make use of the technical content disclosed above to make some changes or modifications to equivalent embodiments with equivalent changes. However, any content that does not deviate from the technical solution of this creation, any simple modifications or equivalent changes to the above embodiments based on the technical essence of this creation And modifications are still within the scope of this authoring technical solution.

no.

Figure 1 is a transmission electron microscope photograph of Example 5; Figure 2 is the TEM-EDS elemental analysis chart of Example 5; 3A to 3D are high-resolution field emission scanning electron microscope photos of Examples 5 to 8, respectively; 4A to 4F are the SEM-EDS element analysis diagrams of Example 5; Figure 5 shows the X-ray diffraction patterns of Examples 5 to 8; FIG. 6A shows the ultraviolet light-visible light-near infrared light absorption analysis results of Example 5, Comparative Example 1, and Comparative Example 2; 6B to 6D are the ultraviolet light-visible light-near infrared light absorption analysis results of Examples 1 to 12, respectively; 7A to 7C are the analysis results of the energy gap curves of Examples 1 to 12, respectively; Fig. 8A is the fluorescence spectra of Example 5, Comparative Example 1, and Comparative Example 2 after being excited by a light source; 8B to 8D are respectively the fluorescence spectra of Examples 1 to 12 after being excited by a light source; 9 shows the cumulative hydrogen production results of Example 5, Comparative Example 1, and Comparative Example 2.

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Claims (10)

A composite photocatalyst material comprising titanium dioxide, gold nano particles and sulfide quantum dots, and the gold nano particles and the sulfide quantum dots are supported on the titanium dioxide; wherein the sulfide quantum dots are lead sulfide quantum dots And zinc sulfide quantum dots, and the molar ratio of the sulfide quantum dots to the titanium dioxide is 0.1:1 to 0.3:1. The composite photocatalyst material according to claim 1, wherein the molar ratio of the sulfide quantum dots to the titanium dioxide is 0.1:1 to 0.2:1. The composite photocatalyst material according to claim 1, wherein the content of the titanium dioxide is taken as 100 parts by weight, and the content of the gold nano particles is 1 part by weight to 3 parts by weight. The composite photocatalyst material according to claim 3, wherein the content of the titanium dioxide is taken as 100 parts by weight, and the content of the gold nanoparticles is 2 to 3 parts by weight. The composite photocatalyst material according to claim 1, wherein the hydrogen production efficiency of the composite photocatalyst material is 3300 micromole/g per hour to 5100 micromole/g per hour. A preparation method of composite photocatalyst material, which comprises the following steps: Step (a): preparing a solution containing titanium dioxide and a chloroauric acid solution, and adding the chloroauric acid solution to the solution containing titanium dioxide at a temperature of 70°C to 90°C to obtain a first mixed solution; Step (b): heating the first mixed solution to 190°C to 210°C and holding the temperature for 7 to 9 hours to obtain a first composite material; Step (c): preparing a lead acetate solution and a zinc acetate solution, mixing the lead acetate solution and the zinc acetate solution, and then adding the first composite material to obtain a second mixed solution; Step (d): After adding sodium sulfide solution to the second mixed solution, a hydrothermal reaction is performed to obtain a second composite material, wherein the reaction temperature of the hydrothermal reaction is 120°C to 180°C, and the reaction time is 23 Hours to 25 hours; and Step (e): drying the second composite material to obtain the composite photocatalyst material; Wherein, the composite photocatalyst material includes titanium dioxide, gold nano particles and sulfide quantum dots, and the gold nano particles and the sulfide quantum dots are supported on the titanium dioxide; the sulfide quantum dots are lead sulfide quantum dots and sulfide quantum dots. Zinc quantum dots, and the molar ratio of the sulfide quantum dots to the titanium dioxide is 0.1:1 to 0.3:1. According to the preparation method described in claim 6, in step (d), the reaction temperature of the hydrothermal reaction is 120°C to 140°C. According to the preparation method described in claim 6, in step (a), the pH value of the solution containing titanium dioxide is 5.5 to 6.5, and the pH value of the chloroauric acid solution is 7.5 to 8.5. According to the preparation method of claim 6, in step (a), the chloroauric acid solution is added to the solution containing titanium dioxide at a rate of 2 ml/min to 3 ml/min. According to the preparation method described in claim 6, in step (d), the addition amount of the sodium sulfide solution is 2.5 to 3 times the volume of the second mixed solution.

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